In order to amplify microwaves or millimeter waves electrically transmitted through a waveguide, or in order to convert the frequency thereof, a waveguide/planar line converter is provided in an interface unit joining a waveguide and a planar line circuit.
Patent Literature 1 discloses a waveguide/planar line converter including a cylindrical waveguide and a planar line substrate furnished on this waveguide.
The planar line substrate includes a laminated structure in the vertical direction. The top layer of the planar circuit substrate is formed in a frame shape compatible with the opening end in the waveguide, and includes a first grounding conductor to which the opening end of this waveguide is adhered and anchored to, and an antenna pattern positioned within the frame of this grounding conductor which comprises a λ/2 resonant antenna.
In addition, the bottom layer of the planar line substrate includes a strip conductor the tip of which extends as far as a position opposite the antenna pattern, and a second grounding conductor positioned surrounding this strip conductor.